cond

cond Macro

Syntax:

cond {↓clause}* → {result}*

clause::=(test-form {form}*)

Arguments and Values:

test-form—a form.

forms—an implicit progn.

results—the values of the forms in the first clause whose test-form yields true, or the primary value of the test-form if there are no forms in that clause, or else nil if no test-form yields true.

Description:

cond allows the execution of forms to be dependent on test-form.

Test-forms are evaluated one at a time in the order in which they are given in the argument list until a test-form is found that evaluates to true.

If there are no forms in that clause, the primary value of the test-form is returned by the cond form. Otherwise, the forms associated with this test-form are evaluated in order, left to right, as an implicit progn, and the values returned by the last form are returned by the cond form.

Once one test-form has yielded true, no additional test-forms are evaluated. If no test-form yields true, nil is returned.

Examples:

(defvar a) → a
(defun select-options () 
  (cond ((= a 1) (setf a 2)) 
	((= a 2) (setf a 3)) 
	((and (= a 3) (floor a 2))) 
	(t (floor a 3)))) → SELECT-OPTIONS 
(setf a 1) → 1 
(select-options) → 2 
a → 2 
(select-options) → 3 
a → 3 
(select-options) → 1 
(setf a 5) → 5 
(select-options) → 1, 2 

See Also:

if, case.

info

We fixed the examples so that it uses defvar to initialize the variable and to use setf rather than setq for assignment.

Expanded Reference: cond

tip

TODO: Please contribute to this page by adding explanations and examples

(cond )